Systems and methods for measuring vehicle speed

Abstract

A system includes a processing module, a sampling module, a period determination module, and a speed determination module. The processing module generates time stamps when pulses are received from a sensor that senses a rotation of a device. The sampling module samples the time stamps during N predetermined intervals and stores N of the time stamps that correspond to the N predetermined intervals, where N is an integer that is greater than 2. The period determination module determines a plurality of periods, wherein each one of the plurality of periods is based on a difference between two of the N time stamps. The speed determination module determines a rotational speed of the device based on a difference between two of the plurality of periods.

1. A system comprising:
 a processing module that generates time stamps when pulses are received from a sensor that senses a rotation of a device; 
 a sampling module that samples the time stamps during N predetermined intervals and that stores N of the time stamps that correspond to the N predetermined intervals, where N is an integer that is greater than 2; 
 a period determination module that determines a plurality of periods, wherein each one of the plurality of periods is based on a difference between two of the N time stamps; and 
 a speed determination module that determines a rotational speed of the device based on a difference between magnitudes of two of the plurality of periods. 
 
     
     
       2. The system of  claim 1  wherein the sensor is one of a crankshaft sensor that senses rotation of a crankshaft, a camshaft sensor that senses rotation of a camshaft, a vehicle speed sensor that senses rotation of an output shaft of a transmission, and a wheel speed sensor that senses rotation of a wheel. 
     
     
       3. The system of  claim 1  wherein each of the N time stamps corresponds to a last pulse received during each of the N predetermined intervals. 
     
     
       4. The system of  claim 1  wherein each one of the plurality of periods is based on a difference between two of the N time stamps from consecutive ones of the N predetermined intervals. 
     
     
       5. The system of  claim 1  wherein the speed determination module determines the difference between two of the plurality of periods based on a longest one of the plurality of periods and a shortest one of the plurality of periods. 
     
     
       6. The system of  claim 1  wherein the speed determination module determines the rotational speed based on a function that relates the rotational speed to the difference between two of the plurality of periods. 
     
     
       7. The system of  claim 1  further comprising a counting module that counts a number of the pulses received from the sensor and that determines a second rotational speed of the device based on the number of the pulses received from the sensor. 
     
     
       8. The system of  claim 7  wherein the speed determination module indicates when a difference between the rotational speed of the device and the second rotational speed of the device is greater than a predetermined threshold. 
     
     
       9. A method comprising:
 in one or more processing modules of a vehicle: 
 generating time stamps when pulses are received from a sensor that senses a rotation of a device; 
 sampling the time stamps during N predetermined intervals; 
 storing N of the time stamps that correspond to the N predetermined intervals, where N is an integer that is greater than 2; 
 determining a plurality of periods, wherein each one of the plurality of periods is based on a difference between two of the N time stamps; 
 determining a rotational speed of the device based on a difference between magnitudes of two of the plurality of periods; and 
 altering an operating parameter of at least one of the vehicle and an engine of the vehicle based on the rotational speed. 
 
     
     
       10. The method of  claim 9  further comprising, in the one or more processing modules of the vehicle, generating time stamps when pulses are received from one of a crankshaft sensor that senses rotation of a crankshaft, a camshaft sensor that senses rotation of a camshaft, a vehicle speed sensor that senses rotation of an output shaft of a transmission, and a wheel speed sensor that senses rotation of a wheel. 
     
     
       11. The method of  claim 9  further comprising, in the one or more processing modules of the vehicle, storing the N time stamps corresponding to last pulses received during the N predetermined intervals. 
     
     
       12. The method of  claim 9  further comprising, in the one or more processing modules of the vehicle, determining each one of the plurality of periods based on a difference between two of the N time stamps from consecutive ones of the N predetermined intervals. 
     
     
       13. The method of  claim 9  further comprising, in the one or more processing modules of the vehicle, determining the difference between two of the plurality of periods based on a longest one of the plurality of periods and a shortest one of the plurality of periods. 
     
     
       14. The method of  claim 9  further comprising, in the one or more processing modules of the vehicle, determining the rotational speed based on a function that relates the rotational speed to the difference between two of the plurality of periods. 
     
     
       15. The method of  claim 9  further comprising, in the one or more processing modules of the vehicle:
 counting a number of the pulses received from the sensor; and 
 determining a second rotational speed of the device based on the number of the pulses received from the sensor. 
 
     
     
       16. The method of  claim 15  further comprising, in the one or more processing modules of the vehicle, indicating when a difference between the rotational speed of the device and the second rotational speed of the device is greater than a predetermined threshold. 
     
     
       17. A system comprising:
 a processing module that generates time stamps when pulses are received from a sensor that senses a rotation of a device; 
 a period determination module that determines a plurality of periods, wherein each one of the plurality of periods is based on a difference between two of the time stamps; and 
 a speed determination module that determines a rotational speed of the device based on a difference between magnitudes of two of the plurality of periods. 
 
     
     
       18. The system of  claim 17  wherein the period determination module determines each one of the plurality of periods based on two of the time stamps that are generated during separate predetermined intervals. 
     
     
       19. The system of  claim 17  wherein the speed determination module determines the difference between two of the plurality of periods based on a longest one of the plurality of periods and a shortest one of the plurality of periods. 
     
     
       20. The system of  claim 18  wherein each of the time stamps corresponds to a last pulse received during each of the predetermined intervals, and wherein each one of the plurality of periods is based on a difference between two of the time stamps from consecutive ones of the predetermined intervals.